The present invention relates to electronic equipment which operates on the basis of a predetermined power source, and a power management method for the electronic equipment, as well as a power source unit which supplies power to electronic equipment body connected to the same via a predetermined bus.
Electronic equipment of the type which use so-called secondary batteries such as lithium ion batteries as power sources, for example, information processing apparatuses such as notebook personal computers, mobile phones or personal digital assistants (PDAs), have recently become popular.
There is a so-called smart battery system (SBS) as a standard for power management in such electronic equipment using a secondary battery as a power source. This smart battery system is a standard for general power management to be mainly used in notebook personal computers or the like. For example, a notebook personal computer is physically roughly divided into a computer body and a battery section, and the smart battery system is applied so that the battery section is constructed to have intelligence.
Specifically, as shown in FIG. 4, a notebook personal computer is constructed to be roughly divided into a battery pack 100 and a computer body 110.
The battery pack 100 is provided with a battery protection IC (Integrated Circuit) 102 as intelligence in addition to a battery 101, and realizes remaining battery power management, charge and discharge current detection as well as the function of protection from overdischarge, overcurrent, overheat and the like, by means of the battery protection IC 102.
The computer body 110 is provided with a CPU (Central Processing Unit) 111 and a peripheral LSI (Large Scale Integration) 112 which realizes various functions, as well as a battery charger 113 serving as a charger, and performs optimum charge and discharge control on the basis of voltage information and current information supplied from the battery 101. In addition, if a smart battery system is applied, the battery charger 113 is also called a smart charger.
In this notebook personal computer, the battery protection IC 102 in the battery pack 100 is connected to a predetermined bus which is called an SM bus (System Management Bus) 120, while the battery charger 113 in the computer body 110 is connected to the SM bus 120 and the CPU 111 is also connected to the SM bus 120 via the peripheral LSI 112, and so-called two-wire half-duplex communication is performed between the battery protection IC 102 and the CPU 111 as well as the battery charger 113.
On the other hand, various power-saving mechanisms have been proposed in order to reduce power consumption and promote efficient use of batteries in various information processing apparatuses such as notebook personal computers, and one example is a method called APM (Advanced Power Management). This APM is intended to reduce power consumption through means adapted to turn off an LCD (Liquid Crystal Display) serving as a display device and change the LCD to an idle mode, if a key input is not performed within a predetermined time.
In embedded applications to be used in mobile electronic equipment and the like, a further approach has been adopted: for example, according to “PowerWise” which is a technique developed by National Semiconductor Corporation and is described in Patent Document 1 (National Semiconductor Corporation, “POWERWISE”, [online], [searched Jul. 3, 2003], Internet<URL:http://www.national.com/appinfo/power/powerwise.html>, a decision is made as to the load of a CPU by an OS (Operating System) on the basis of the amount of task work and scheduling such as task cueing, and a clock speed and/or a voltage to execute the work is set to realize supply of necessary and sufficient energy so as to promote a reduction of power consumption.
Furthermore, a similar technique is described in Patent Document 1 (Japanese Patent Application Publication No. 2002-91638), and the technique proposes a method in which an OS determines the status of a task and stops the clocks of peripheral devices or circuits to reduce power consumption.
Specifically, Patent Document 1 discloses a power consumption reduction system and a power consumption reduction method, both of which cause an arithmetic processing unit to operate during only the period in which there exists a task to be executed by the arithmetic processing unit and during only the period of an interrupt to the arithmetic processing unit in an information processing apparatus which time-shares a plurality of tasks, sequentially allocates the tasks to the arithmetic processing unit, and performs apparently parallel processing of the tasks. Patent Document 1 states that the method is capable of reducing power consumption without deteriorating a processing speed as viewed from a user while the user is actually using the information processing apparatus.
In addition, a fuel cell has recently been known which is supplied with a fuel gas containing a large amount of hydrogen or a fuel fluid and with oxygen (air) as an oxidizer gas and causes the fuel gas or the fuel fluid and the oxidizer gas to electrochemically react with each other so as to obtain generated power. For example, there is a fuel cell having a structure in which a proton conductor membrane serving as an electrolyte membrane is clamped between a fuel electrode and an air electrode.
Such a fuel cell is highly expected to be applied to electric vehicles or hybrid vehicles by being incorporated into vehicles such as automobiles as power sources, and in addition, because of its structure easy to reduce in weight and size, there are attempts to apply the fuel cell to power sources for various information processing apparatuses such as notebook personal computers, mobile phones or personal digital assistants. In addition, power generated by fuel cells for domestic or personal uses is supplied to electric appliances such as home information appliances.
However, as to fuel cells, there does not at all exist a power management standard like the above-mentioned one for secondary batteries, and if such fuel cells are to be used as power sources for various electronic equipment serving as auxiliary machines, it is completely unclear what control is to be carried out.